Takasu, N. N., Pendergast, J. S., Olivas, C. S., Yamazaki, S., & Nakamura, W. In vivo monitoring of multi-unit neural activity in the suprachiasmatic nucleus reveals robust circadian rhythms in Period1⁻/⁻ mice. Plos One, 8(5), e64333. https://doi.org/10.1371/journal.pone.0064333(Original work published 2013)